While a healthy and hoped-for pregnancy is a joyous occasion at any age, it is especially in a woman’s late 40s; doctors refer to a woman over the age of 35 as of “advanced maternal age,” with the attendant risks and difficult odds that accompany that designation. Here’s everything you need to know about the likelihood of getting pregnant in your late 40s (and into your 50s, like Nielsen).

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What Age Does Fertility Start to Decline?

Weisz’s pregnancy could be considered a miracle, says Dr. Zev Williams, MD, PhD, Chief of the Division of Reproductive Endocrinology and Infertility and Associate Professor of Obstetrics and Gynecology at Columbia University Fertility Center.

“The more we study it, the more we think to conceive at any age and to have a healthy pregnancy is a miracle. It really is an incredible process,” says Williams. “I wouldn’t say there’s one age where, the year before it’s not a miracle [to conceive naturally] and after that it is, but for a woman after age 42, 43, you’re looking at well under 1 percent chances.”

However, thanks to modern technology, there are a variety of assisted reproductive options that significantly improve the chances of a later pregnancy. “A woman over age 45 who uses donor eggs, her own eggs that she froze earlier, or even donor embryos would have a very high chance of success,” Williams says. “Ultimately I’d put it at well over a 75 percent chance with donor eggs or embryos.”

But natural fertility decline begins much earlier than your 40s. “By the numbers, there is a steady [fertility] decline,” he explains. “From age 18 up until age 30, it’s sort of a gradual decline. After age 35 the rate of decline accelerates, and after age 40 or 42, it accelerates much faster. So there really isn’t a big difference in the chance of getting pregnant and having a successful pregnancy for a woman in her 20s or early 30s, but by the time you start looking at the late 30s and early 40s, every few months can make a difference.”

Williams explains that the reason for that is women are born with all the eggs they’ll ever have, which stay “arrested” until they’re ovulated. So the older a woman is when she tries to have a baby, the more likely it is that there could be chromosomal problems in the egg.

“The most common [method is] to use donor eggs, and that’s when you get eggs from a woman who is matched to you—similar background, similar appearance—but who is younger,” Williams says. “Eggs are taken from that woman, fertilized with the partner or donor sperm, and then transferred and placed into the uterus of the intended mother.”

To get pregnant naturally after your mid-40s would require “a healthy dose of good luck,” he says. “I think…to conceive naturally, meaning without the assistance of IVF and assisted reproductive technologies, is very, very unlikely.”

IVF technology has improved over the past decade, so for a woman hoping to carry her own egg, there are options, but they do require some advance planning.

“What matters in terms of the likelihood of success isn’t the mother’s age, it’s the age at which she was when she froze her eggs,” Williams explains. “The challenge is that when a woman is in her 20s, she’s not thinking that she’s going to need to use eggs when she’s in her 40s. But when she’s in her 40s and wants to freeze her eggs, it’s more difficult at that point to get a healthy egg. It’s a good idea to freeze eggs sooner rather than later. When you’re younger it’s easier to get more eggs, and those eggs that you get are more likely to be healthy.”

Halle Berry and baby Maceo

Halle Berry/Instagram

How Does Egg Donation and IVF Work?

“The process is actually pretty good,” says Williams. “A lot of younger women have already come to us and said they are interested in helping others have children and would like to be egg donors, so we have their profiles available. And then when someone comes intending to get pregnant and would like to use donor eggs, we can fairly quickly match them up with an appropriate donor.”

“Then the donor would go through the first part of the IVF cycle to have eggs removed, they’d be fertilized with the partner’s sperm, and then transferred into the intended mother,” he says. “Often there’s extra embryos available that can be frozen so that the intended mother can have additional siblings in the future.”

As technology has developed, it has become easier to very carefully match the intended mothers with an egg donor who closely resembles them. “We can get pretty good at getting patients egg donors who resemble the intended mothers—similar height, hair color, skin color, eye color, etc.,” he says.

IVF (in vitro fertilization) is another popular method, which “essentially mimics what happens in a natural menstrual cycle, but sort of ramped up a little bit in terms of the egg production,” explains Williams.

“In a normal cycle, it takes about two weeks for an egg to be produced, then it’s ovulated, fertilized, and implanted, so that by the time of the upcoming period, the woman would know she’s pregnant,” he says. “With IVF it’s similar, but instead of one egg being produced, a group of eggs are produced… fertilization happens in the lab and then the embryo is put back into the uterus at the same time when a naturally conceived embryo would be arriving in the uterus.”

What Are the Risks of Fertility Treatments?

Williams says that in general, egg donation poses less of a risk to mothers than IVF. “The risks with egg donation are actually quite minimal, [while] the main risk we worry about in women who are going through assisted reproductive technology is higher-order multiples,” he says, referring to women who end up pregnant with triplets or more.

That’s because donor eggs are more likely to be chromosomally normal so doctors only transfer one at a time, while women over the age of 40 who go through IVF “would typically need to have the embryos genetically tested before they’re put in to make sure they’re healthy. If she doesn’t do that there’s often more embryos put in, because there’s a very low likelihood that they would all be normal,” thus leading to the risk of having multiples.

Thinking about becoming famous and having a child at 50? You’re in luck, Williams says: “Egg freezing technology has really advanced a lot…which means the success for that has improved a lot, and so that’s becoming an option more and more for young women to do when they’re thinking about the future.”

But some women may have missed the window to freeze their eggs, as even as recently as 10 years ago the process was still considered experimental.

“So right now, for older women who want to conceive, they would typically either try going through IVF and [hope] to get healthy embryos, or [they] would use donor eggs.”

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